-Make message __deepcopy__ call UPB code instead of default implementation for python UPB (splitted change 1)

PiperOrigin-RevId: 528083849

python/google/protobuf/internal/message_test.py

@@ -1409,6 +1409,10 @@ class Proto2Test(unittest.TestCase):
     self.assertEqual(all_set, golden_message)
     self.assertEqual(golden_data, golden_message.SerializeToString())
     golden_copy = copy.deepcopy(golden_message)
+    self.assertEqual(golden_message, golden_copy)
+    # Depend on a specific serialization order for extensions is not
+    # reasonable to guarantee.
+    if api_implementation.Type() != 'upb':
       self.assertEqual(golden_data, golden_copy.SerializeToString())
 
   def testGoldenPackedExtensions(self):
@@ -1420,6 +1424,10 @@ class Proto2Test(unittest.TestCase):
     self.assertEqual(all_set, golden_message)
     self.assertEqual(golden_data, all_set.SerializeToString())
     golden_copy = copy.deepcopy(golden_message)
+    self.assertEqual(golden_message, golden_copy)
+    # Depend on a specific serialization order for extensions is not
+    # reasonable to guarantee.
+    if api_implementation.Type() != 'upb':
       self.assertEqual(golden_data, golden_copy.SerializeToString())
 
   def testPickleIncompleteProto(self):